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changes in the underlying JavaScript engine and allow modules
compiled for one version to run on later versions of Node.js without
recompilation.
Addons are built/packaged with the same approach/tools
outlined in the section titled [C++ Addons](addons.html).
The only difference is the set of APIs that are used by the native code.
Instead of using the V8 or [Native Abstractions for Node.js][] APIs,
the functions available in the N-API are used.
APIs exposed by N-API are generally used to create and manipulate
JavaScript values. Concepts and operations generally map to ideas specified
in the ECMA262 Language Specification. The APIs have the following
properties:
- All N-API calls return a status code of type `napi_status`. This
status indicates whether the API call succeeded or failed.
- The API's return value is passed via an out parameter.
- All JavaScript values are abstracted behind an opaque type named
`napi_value`.
- In case of an error status code, additional information can be obtained
using `napi_get_last_error_info`. More information can be found in the error
handling section [Error Handling][].
The documentation for N-API is structured as follows:
* [Basic N-API Data Types][]
* [Error Handling][]
* [Object Lifetime Management][]
* [Module Registration][]
* [Working with JavaScript Values][]
* [Working with JavaScript Values - Abstract Operations][]
* [Working with JavaScript Properties][]
* [Working with JavaScript Functions][]
* [Object Wrap][]
* [Simple Asynchronous Operations][]
* [Custom Asynchronous Operations][]
* [Promises][]
* [Script Execution][]
The N-API is a C API that ensures ABI stability across Node.js versions
and different compiler levels. However, we also understand that a C++
API can be easier to use in many cases. To support these cases we expect
there to be one or more C++ wrapper modules that provide an inlineable C++
API. Binaries built with these wrapper modules will depend on the symbols
for the N-API C based functions exported by Node.js. These wrappers are not
part of N-API, nor will they be maintained as part of Node.js. One such
example is: [node-api](https://github.com/nodejs/node-api).
In order to use the N-API functions, include the file
[node_api.h](https://github.com/nodejs/node/blob/master/src/node_api.h)
which is located in the src directory in the node development tree.
For example:
```C
```
N-API exposes the following fundamental datatypes as abstractions that are
consumed by the various APIs. These APIs should be treated as opaque,
introspectable only with other N-API calls.
Integral status code indicating the success or failure of a N-API call.
Currently, the following status codes are supported.
```C
typedef enum {
napi_ok,
napi_invalid_arg,
napi_object_expected,
napi_string_expected,
napi_name_expected,
napi_function_expected,
napi_number_expected,
napi_boolean_expected,
napi_array_expected,
napi_generic_failure,
napi_pending_exception,
napi_cancelled,
napi_status_last
} napi_status;
```
If additional information is required upon an API returning a failed status,
it can be obtained by calling `napi_get_last_error_info`.
```C
typedef struct {
const char* error_message;
void* engine_reserved;
uint32_t engine_error_code;
napi_status error_code;
} napi_extended_error_info;
```
- `error_message`: UTF8-encoded string containing a VM-neutral description of
the error.
- `engine_reserved`: Reserved for VM-specific error details. This is currently
not implemented for any VM.
- `engine_error_code`: VM-specific error code. This is currently
not implemented for any VM.
- `error_code`: The N-API status code that originated with the last error.
See the [Error Handling][] section for additional information.
`napi_env` is used to represent a context that the underlying N-API
implementation can use to persist VM-specific state. This structure is passed
to native functions when they're invoked, and it must be passed back when
making N-API calls. Specifically, the same `napi_env` that was passed in when
the initial native function was called must be passed to any subsequent
nested N-API calls. Caching the `napi_env` for the purpose of general reuse is
not allowed.
This is an opaque pointer that is used to represent a JavaScript value.
This is an abstraction used to control and modify the lifetime of objects
created within a particular scope. In general, N-API values are created within
the context of a handle scope. When a native method is called from
JavaScript, a default handle scope will exist. If the user does not explicitly
create a new handle scope, N-API values will be created in the default handle
scope. For any invocations of code outside the execution of a native method
(for instance, during a libuv callback invocation), the module is required to
create a scope before invoking any functions that can result in the creation
of JavaScript values.
Handle scopes are created using [`napi_open_handle_scope`][] and are destroyed
using [`napi_close_handle_scope`][]. Closing the scope can indicate to the GC that
all `napi_value`s created during the lifetime of the handle scope are no longer
referenced from the current stack frame.
For more details, review the [Object Lifetime Management][].
Escapable handle scopes are a special type of handle scope to return values
created within a particular handle scope to a parent scope.
This is the abstraction to use to reference a `napi_value`. This allows for
users to manage the lifetimes of JavaScript values, including defining their
minimum lifetimes explicitly.
For more details, review the [Object Lifetime Management][].
Opaque datatype that is passed to a callback function. It can be used for
getting additional information about the context in which the callback was
invoked.
Function pointer type for user-provided native functions which are to be
exposed to JavaScript via N-API. Callback functions should satisfy the
following signature:
```C
typedef napi_value (*napi_callback)(napi_env, napi_callback_info);
```
Function pointer type for add-on provided functions that allow the user to be
notified when externally-owned data is ready to be cleaned up because the
object with which it was associated with, has been garbage-collected. The user
must provide a function satisfying the following signature which would get
called upon the object's collection. Currently, `napi_finalize` can be used for
finding out when objects that have external data are collected.
```C
typedef void (*napi_finalize)(napi_env env,
void* finalize_data,
void* finalize_hint);
```
Function pointer used with functions that support asynchronous
operations. Callback functions must statisfy the following signature:
```C
typedef void (*napi_async_execute_callback)(napi_env env, void* data);
```
Function pointer used with functions that support asynchronous
operations. Callback functions must statisfy the following signature:
```C
typedef void (*napi_async_complete_callback)(napi_env env,
napi_status status,
void* data);
```
N-API uses both return values and Javascript exceptions for error handling.
The following sections explain the approach for each case.
All of the N-API functions share the same error handling pattern. The
return type of all API functions is `napi_status`.
The return value will be `napi_ok` if the request was successful and
no uncaught JavaScript exception was thrown. If an error occurred AND
an exception was thrown, the `napi_status` value for the error
will be returned. If an exception was thrown, and no error occurred,
`napi_pending_exception` will be returned.
In cases where a return value other than `napi_ok` or
`napi_pending_exception` is returned, [`napi_is_exception_pending`][]
must be called to check if an exception is pending.
See the section on exceptions for more details.
The full set of possible napi_status values is defined
in `napi_api_types.h`.
The `napi_status` return value provides a VM-independent representation of
the error which occurred. In some cases it is useful to be able to get
more detailed information, including a string representing the error as well as
VM (engine)-specific information.
In order to retrieve this information [`napi_get_last_error_info`][]
is provided which returns a `napi_extended_error_info` structure.
The format of the `napi_extended_error_info` structure is as follows:
```C
typedef struct napi_extended_error_info {
const char* error_message;
void* engine_reserved;
uint32_t engine_error_code;
napi_status error_code;
};
```
- `error_message`: Textual representation of the error that occurred.
- `engine_reserved`: Opaque handle reserved for engine use only.
- `engine_error_code`: VM specific error code.
- `error_code`: n-api status code for the last error.
[`napi_get_last_error_info`][] returns the information for the last
N-API call that was made.
*Note*: Do not rely on the content or format of any of the extended
information as it is not subject to SemVer and may change at any time.
It is intended only for logging purposes.
<!-- YAML
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```C
napi_status
napi_get_last_error_info(napi_env env,
const napi_extended_error_info** result);
```
- `[in] env`: The environment that the API is invoked under.
- `[out] result`: The `napi_extended_error_info` structure with more
information about the error.
Returns `napi_ok` if the API succeeded.
This API retrieves a `napi_extended_error_info` structure with information
about the last error that occurred.
*Note*: The content of the `napi_extended_error_info` returned is only
valid up until an n-api function is called on the same `env`.
*Note*: Do not rely on the content or format of any of the extended
information as it is not subject to SemVer and may change at any time.
It is intended only for logging purposes.
Any N-API function call may result in a pending JavaScript exception. This is
obviously the case for any function that may cause the execution of
JavaScript, but N-API specifies that an exception may be pending
on return from any of the API functions.
If the `napi_status` returned by a function is `napi_ok` then no
exception is pending and no additional action is required. If the
`napi_status` returned is anything other than `napi_ok` or
`napi_pending_exception`, in order to try to recover and continue
instead of simply returning immediately, [`napi_is_exception_pending`][]
must be called in order to determine if an exception is pending or not.
When an exception is pending one of two approaches can be employed.
The first approach is to do any appropriate cleanup and then return so that
execution will return to JavaScript. As part of the transition back to
JavaScript the exception will be thrown at the point in the JavaScript
code where the native method was invoked. The behavior of most N-API calls
is unspecified while an exception is pending, and many will simply return
`napi_pending_exception`, so it is important to do as little as possible
and then return to JavaScript where the exception can be handled.
The second approach is to try to handle the exception. There will be cases
where the native code can catch the exception, take the appropriate action,
and then continue. This is only recommended in specific cases
where it is known that the exception can be safely handled. In these
cases [`napi_get_and_clear_last_exception`][] can be used to get and
clear the exception. On success, result will contain the handle to
the last JavaScript Object thrown. If it is determined, after
retrieving the exception, the exception cannot be handled after all
it can be re-thrown it with [`napi_throw`][] where error is the
JavaScript Error object to be thrown.
The following utility functions are also available in case native code
needs to throw an exception or determine if a `napi_value` is an instance
of a JavaScript `Error` object: [`napi_throw_error`][],
[`napi_throw_type_error`][], [`napi_throw_range_error`][] and
[`napi_is_error`][].
The following utility functions are also available in case native
code needs to create an Error object: [`napi_create_error`][],
[`napi_create_type_error`][], and [`napi_create_range_error`][].
where result is the napi_value that refers to the newly created
JavaScript Error object.
The Node.js project is adding error codes to all of the errors
generated internally. The goal is for applications to use these
error codes for all error checking. The associated error messages
will remain, but will only be meant to be used for logging and
display with the expectation that the message can change without
SemVer applying. In order to support this model with N-API, both
in internal functionality and for module specific functionality
(as its good practice), the `throw_` and `create_` functions
take an optional code parameter which is the string for the code
to be added to the error object. If the optional parameter is NULL
then no code will be associated with the error. If a code is provided,
the name associated with the error is also updated to be:
```text
originalName [code]
```
where originalName is the original name associated with the error
and code is the code that was provided. For example if the code
is 'ERR_ERROR_1' and a TypeError is being created the name will be:
```text
TypeError [ERR_ERROR_1]
```
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```C
NODE_EXTERN napi_status napi_throw(napi_env env, napi_value error);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] error`: The `napi_value` for the Error to be thrown.
Returns `napi_ok` if the API succeeded.
This API throws the JavaScript Error provided.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_throw_error(napi_env env,
const char* code,
const char* msg);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] code`: Optional error code to be set on the error.
- `[in] msg`: C string representing the text to be associated with
the error.
Returns `napi_ok` if the API succeeded.
This API throws a JavaScript Error with the text provided.
<!-- YAML
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```C
NODE_EXTERN napi_status napi_throw_type_error(napi_env env,
const char* code,
const char* msg);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] code`: Optional error code to be set on the error.
- `[in] msg`: C string representing the text to be associated with
the error.
Returns `napi_ok` if the API succeeded.
This API throws a JavaScript TypeError with the text provided.
<!-- YAML
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```C
NODE_EXTERN napi_status napi_throw_range_error(napi_env env,
const char* code,
const char* msg);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] code`: Optional error code to be set on the error.
- `[in] msg`: C string representing the text to be associated with
the error.
Returns `napi_ok` if the API succeeded.
This API throws a JavaScript RangeError with the text provided.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_is_error(napi_env env,
napi_value value,
bool* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] msg`: The `napi_value` to be checked.
- `[out] result`: Boolean value that is set to true if `napi_value` represents
an error, false otherwise.
Returns `napi_ok` if the API succeeded.
This API queries a `napi_value` to check if it represents an error object.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_create_error(napi_env env,
napi_value code,
napi_value msg,
napi_value* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] code`: Optional `napi_value` with the string for the error code to
be associated with the error.
- `[in] msg`: napi_value that references a JavaScript String to be
used as the message for the Error.
- `[out] result`: `napi_value` representing the error created.
Returns `napi_ok` if the API succeeded.
This API returns a JavaScript Error with the text provided.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_create_type_error(napi_env env,
napi_value code,
napi_value msg,
napi_value* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] code`: Optional `napi_value` with the string for the error code to
be associated with the error.
- `[in] msg`: napi_value that references a JavaScript String to be
used as the message for the Error.
- `[out] result`: `napi_value` representing the error created.
Returns `napi_ok` if the API succeeded.
This API returns a JavaScript TypeError with the text provided.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_create_range_error(napi_env env,
napi_value code,
const char* msg,
napi_value* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] code`: Optional `napi_value` with the string for the error code to
be associated with the error.
- `[in] msg`: napi_value that references a JavaScript String to be
used as the message for the Error.
- `[out] result`: `napi_value` representing the error created.
Returns `napi_ok` if the API succeeded.
This API returns a JavaScript RangeError with the text provided.
<!-- YAML
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```C
napi_status napi_get_and_clear_last_exception(napi_env env,
napi_value* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[out] result`: The exception if one is pending, NULL otherwise.
Returns `napi_ok` if the API succeeded.
This API returns true if an exception is pending.
<!-- YAML
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```C
napi_status napi_is_exception_pending(napi_env env, bool* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[out] result`: Boolean value that is set to true if an exception is pending.
Returns `napi_ok` if the API succeeded.
This API returns true if an exception is pending.
In the event of an unrecoverable error in a native module, a fatal error can be
thrown to immediately terminate the process.
<!-- YAML
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```C
NAPI_NO_RETURN void napi_fatal_error(const char* location,
size_t location_len,
const char* message,
size_t message_len);
```
- `[in] location`: Optional location at which the error occurred.
- `[in] location_len`: The length of the location in bytes, or
NAPI_AUTO_LENGTH if it is null-terminated.
- `[in] message`: The message associated with the error.
- `[in] message_len`: The length of the message in bytes, or
NAPI_AUTO_LENGTH if it is
null-terminated.
The function call does not return, the process will be terminated.
As N-API calls are made, handles to objects in the heap for the underlying
VM may be returned as `napi_values`. These handles must hold the
objects 'live' until they are no longer required by the native code,
otherwise the objects could be collected before the native code was
finished using them.
As object handles are returned they are associated with a
'scope'. The lifespan for the default scope is tied to the lifespan
of the native method call. The result is that, by default, handles
remain valid and the objects associated with these handles will be
held live for the lifespan of the native method call.
In many cases, however, it is necessary that the handles remain valid for
either a shorter or longer lifespan than that of the native method.
The sections which follow describe the N-API functions than can be used
to change the handle lifespan from the default.
It is often necessary to make the lifespan of handles shorter than
the lifespan of a native method. For example, consider a native method
that has a loop which iterates through the elements in a large array:
```C
for (int i = 0; i < 1000000; i++) {
napi_value result;
napi_status status = napi_get_element(e object, i, &result);
if (status != napi_ok) {
break;
}
// do something with element
}
```
This would result in a large number of handles being created, consuming
substantial resources. In addition, even though the native code could only
use the most recent handle, all of the associated objects would also be
kept alive since they all share the same scope.
To handle this case, N-API provides the ability to establish a new 'scope' to
which newly created handles will be associated. Once those handles
are no longer required, the scope can be 'closed' and any handles associated
with the scope are invalidated. The methods available to open/close scopes are
[`napi_open_handle_scope`][] and [`napi_close_handle_scope`][].
N-API only supports a single nested hiearchy of scopes. There is only one
active scope at any time, and all new handles will be associated with that
scope while it is active. Scopes must be closed in the reverse order from
which they are opened. In addition, all scopes created within a native method
must be closed before returning from that method.
Taking the earlier example, adding calls to [`napi_open_handle_scope`][] and
[`napi_close_handle_scope`][] would ensure that at most a single handle
is valid throughout the execution of the loop:
```C
for (int i = 0; i < 1000000; i++) {
napi_handle_scope scope;
napi_status status = napi_open_handle_scope(env, &scope);
if (status != napi_ok) {
break;
}
napi_value result;
status = napi_get_element(e object, i, &result);
if (status != napi_ok) {
break;
}
// do something with element
status = napi_close_handle_scope(env, scope);
if (status != napi_ok) {
break;
}
}
```
When nesting scopes, there are cases where a handle from an
inner scope needs to live beyond the lifespan of that scope. N-API supports an
'escapable scope' in order to support this case. An escapable scope
allows one handle to be 'promoted' so that it 'escapes' the
current scope and the lifespan of the handle changes from the current
scope to that of the outer scope.
The methods available to open/close escapable scopes are
[`napi_open_escapable_handle_scope`][] and [`napi_close_escapable_handle_scope`][].
The request to promote a handle is made through [`napi_escape_handle`][] which
can only be called once.
<!-- YAML
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```C
NODE_EXTERN napi_status napi_open_handle_scope(napi_env env,
napi_handle_scope* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[out] result`: `napi_value` representing the new scope.
Returns `napi_ok` if the API succeeded.
This API open a new scope.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_close_handle_scope(napi_env env,
napi_handle_scope scope);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] scope`: `napi_value` representing the scope to be closed.
Returns `napi_ok` if the API succeeded.
This API closes the scope passed in. Scopes must be closed in the
reverse order from which they were created.
<!-- YAML
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```C
NODE_EXTERN napi_status
napi_open_escapable_handle_scope(napi_env env,
napi_handle_scope* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[out] result`: `napi_value` representing the new scope.
Returns `napi_ok` if the API succeeded.
This API open a new scope from which one object can be promoted
to the outer scope.
<!-- YAML
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```C
NODE_EXTERN napi_status
napi_close_escapable_handle_scope(napi_env env,
napi_handle_scope scope);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] scope`: `napi_value` representing the scope to be closed.
Returns `napi_ok` if the API succeeded.
This API closes the scope passed in. Scopes must be closed in the
reverse order from which they were created.
<!-- YAML
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```C
napi_status napi_escape_handle(napi_env env,
napi_escapable_handle_scope scope,
napi_value escapee,
napi_value* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] scope`: `napi_value` representing the current scope.
- `[in] escapee`: `napi_value` representing the JavaScript Object to be escaped.
- `[out] result`: `napi_value` representing the handle to the escaped
Object in the outer scope.
Returns `napi_ok` if the API succeeded.
This API promotes the handle to the JavaScript object so that it is valid
for the lifetime of the outer scope. It can only be called once per scope.
If it is called more than once an error will be returned.
In some cases an addon will need to be able to create and reference objects
with a lifespan longer than that of a single native method invocation. For
example, to create a constructor and later use that constructor
in a request to creates instances, it must be possible to reference
the constructor object across many different instance creation requests. This
would not be possible with a normal handle returned as a `napi_value` as
described in the earlier section. The lifespan of a normal handle is
managed by scopes and all scopes must be closed before the end of a native
method.
N-API provides methods to create persistent references to an object.
Each persistent reference has an associated count with a value of 0
or higher. The count determines if the reference will keep
the corresponding object live. References with a count of 0 do not
prevent the object from being collected and are often called 'weak'
references. Any count greater than 0 will prevent the object
from being collected.
References can be created with an initial reference count. The count can
then be modified through [`napi_reference_ref`][] and
[`napi_reference_unref`][]. If an object is collected while the count
for a reference is 0, all subsequent calls to
get the object associated with the reference [`napi_get_reference_value`][]
will return NULL for the returned `napi_value`. An attempt to call
[`napi_reference_ref`][] for a reference whose object has been collected
will result in an error.
References must be deleted once they are no longer required by the addon. When
a reference is deleted it will no longer prevent the corresponding object from
being collected. Failure to delete a persistent reference will result in
a 'memory leak' with both the native memory for the persistent reference and
the corresponding object on the heap being retained forever.
There can be multiple persistent references created which refer to the same
object, each of which will either keep the object live or not based on its
individual count.
<!-- YAML
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```C
NODE_EXTERN napi_status napi_create_reference(napi_env env,
napi_value value,
int initial_refcount,
napi_ref* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing the Object to which we want
a reference.
- `[in] initial_refcount`: Initial reference count for the new reference.
- `[out] result`: `napi_ref` pointing to the new reference.
Returns `napi_ok` if the API succeeded.
This API create a new reference with the specified reference count
to the Object passed in.
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```C
NODE_EXTERN napi_status napi_delete_reference(napi_env env, napi_ref ref);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] ref`: `napi_ref` to be deleted.
Returns `napi_ok` if the API succeeded.
This API deletes the reference passed in.
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```C
NODE_EXTERN napi_status napi_reference_ref(napi_env env,
napi_ref ref,
int* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] ref`: `napi_ref` for which the reference count will be incremented.
- `[out] result`: The new reference count.
Returns `napi_ok` if the API succeeded.
This API increments the reference count for the reference
passed in and returns the resulting reference count.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_reference_unref(napi_env env,
napi_ref ref,
int* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] ref`: `napi_ref` for which the reference count will be decremented.
- `[out] result`: The new reference count.
Returns `napi_ok` if the API succeeded.
This API decrements the reference count for the reference
passed in and returns the resulting reference count.
<!-- YAML
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-->
```C
NODE_EXTERN napi_status napi_get_reference_value(napi_env env,
napi_ref ref,
napi_value* result);
```
the `napi_value passed` in or out of these methods is a handle to the
object to which the reference is related.
- `[in] env`: The environment that the API is invoked under.
- `[in] ref`: `napi_ref` for which we requesting the corresponding Object.
- `[out] result`: The `napi_value` for the Object referenced by the
`napi_ref`.
Returns `napi_ok` if the API succeeded.
If still valid, this API returns the `napi_value` representing the
JavaScript Object associated with the `napi_ref`. Otherise, result
will be NULL.
N-API modules are registered in a manner similar to other modules
except that instead of using the `NODE_MODULE` macro the following
is used:
```C
NAPI_MODULE(NODE_GYP_MODULE_NAME, Init)
```
The next difference is the signature for the `Init` method. For a N-API
module it is as follows:
```C
napi_value Init(napi_env env, napi_value exports);
```
The return value from `Init` is treated as the `exports` object for the module.
The `Init` method is passed an empty object via the `exports` parameter as a
convenience. If `Init` returns NULL, the parameter passed as `exports` is
exported by the module. N-API modules cannot modify the `module` object but can
specify anything as the `exports` property of the module.
For example, to add the method `hello` as a function so that it can be called
as a method provided by the addon:
```C
napi_value Init(napi_env env, napi_value exports) {
napi_status status;
napi_property_descriptor desc =
{"hello", Method, 0, 0, 0, napi_default, 0};
if (status != napi_ok) return nullptr;
status = napi_define_properties(env, exports, 1, &desc);
if (status != napi_ok) return nullptr;
return exports;
}
```
For example, to set a function to be returned by the `require()` for the addon:
```C
napi_value Init(napi_env env, napi_value exports) {
napi_value method;
napi_status status;
status = napi_create_function(env, "exports", Method, NULL, &method));
if (status != napi_ok) return nullptr;
return method;
}
```
For example, to define a class so that new instances can be created
(often used with [Object Wrap][]):
```C
// NOTE: partial example, not all referenced code is included
napi_value Init(napi_env env, napi_value exports) {
napi_status status;
napi_property_descriptor properties[] = {
{ "value", nullptr, GetValue, SetValue, 0, napi_default, 0 },
DECLARE_NAPI_METHOD("plusOne", PlusOne),
DECLARE_NAPI_METHOD("multiply", Multiply),
};
napi_value cons;
status =
napi_define_class(env, "MyObject", New, nullptr, 3, properties, &cons);
if (status != napi_ok) return nullptr;
status = napi_create_reference(env, cons, 1, &constructor);
if (status != napi_ok) return nullptr;
status = napi_set_named_property(env, exports, "MyObject", cons);
if (status != napi_ok) return nullptr;
return exports;
}
```
For more details on setting properties on objects, see the section on
[Working with JavaScript Properties][].
For more details on building addon modules in general, refer to the existing API
N-API exposes a set of APIs to create all types of JavaScript values.
Some of these types are documented under
[Section 6](https://tc39.github.io/ecma262/#sec-ecmascript-data-types-and-values)
of the [ECMAScript Language Specification][].
Fundamentally, these APIs are used to do one of the following:
1. Create a new JavaScript object
2. Convert from a primitive C type to an N-API value
3. Convert from N-API value to a primitive C type
4. Get global instances including `undefined` and `null`
N-API values are represented by the type `napi_value`.
Any N-API call that requires a JavaScript value takes in a `napi_value`.
In some cases, the API does check the type of the `napi_value` up-front.
However, for better performance, it's better for the caller to make sure that
the `napi_value` in question is of the JavaScript type expected by the API.
```C
typedef enum {
// ES6 types (corresponds to typeof)
napi_undefined,
napi_null,
napi_boolean,
napi_number,
napi_string,
napi_symbol,
napi_object,
napi_function,
napi_external,
} napi_valuetype;
```
Describes the type of a `napi_value`. This generally corresponds to the types
described in
[Section 6.1](https://tc39.github.io/ecma262/#sec-ecmascript-language-types) of
the ECMAScript Language Specification.
In addition to types in that section, `napi_valuetype` can also represent
Functions and Objects with external data.
```C
typedef enum {
napi_int8_array,
napi_uint8_array,
napi_uint8_clamped_array,
napi_int16_array,
napi_uint16_array,
napi_int32_array,
napi_uint32_array,
napi_float32_array,
napi_float64_array,
} napi_typedarray_type;
```
This represents the underlying binary scalar datatype of the TypedArray.
Elements of this enum correspond to
[Section 22.2](https://tc39.github.io/ecma262/#sec-typedarray-objects)
of the [ECMAScript Language Specification][].
<!-- YAML
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-->
```C
napi_status napi_create_array(napi_env env, napi_value* result)
```
- `[in] env`: The environment that the N-API call is invoked under.
- `[out] result`: A `napi_value` representing a JavaScript Array.
Returns `napi_ok` if the API succeeded.
This API returns an N-API value corresponding to a JavaScript Array type.
JavaScript arrays are described in
[Section 22.1](https://tc39.github.io/ecma262/#sec-array-objects) of the
ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_array_with_length(napi_env env,
size_t length,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] length`: The initial length of the Array.
- `[out] result`: A `napi_value` representing a JavaScript Array.
Returns `napi_ok` if the API succeeded.
This API returns an N-API value corresponding to a JavaScript Array type.
The Array's length property is set to the passed-in length parameter.
However, the underlying buffer is not guaranteed to be pre-allocated by the VM
when the array is created - that behavior is left to the underlying VM
implementation.
If the buffer must be a contiguous block of memory that can be
directly read and/or written via C, consider using
[`napi_create_external_arraybuffer`][].
JavaScript arrays are described in
[Section 22.1](https://tc39.github.io/ecma262/#sec-array-objects) of the
ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_arraybuffer(napi_env env,
size_t byte_length,
void** data,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] length`: The length in bytes of the array buffer to create.
- `[out] data`: Pointer to the underlying byte buffer of the ArrayBuffer.
- `[out] result`: A `napi_value` representing a JavaScript ArrayBuffer.
Returns `napi_ok` if the API succeeded.
This API returns an N-API value corresponding to a JavaScript ArrayBuffer.
ArrayBuffers are used to represent fixed-length binary data buffers. They are
normally used as a backing-buffer for TypedArray objects.
The ArrayBuffer allocated will have an underlying byte buffer whose size is
determined by the `length` parameter that's passed in.
The underlying buffer is optionally returned back to the caller in case the
caller wants to directly manipulate the buffer. This buffer can only be
written to directly from native code. To write to this buffer from JavaScript,
a typed array or DataView object would need to be created.
JavaScript ArrayBuffer objects are described in
[Section 24.1](https://tc39.github.io/ecma262/#sec-arraybuffer-objects)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_buffer(napi_env env,
size_t size,
void** data,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] size`: Size in bytes of the underlying buffer.
- `[out] data`: Raw pointer to the underlying buffer.
- `[out] result`: A `napi_value` representing a `node::Buffer`.
Returns `napi_ok` if the API succeeded.
This API allocates a `node::Buffer` object. While this is still a
fully-supported data structure, in most cases using a TypedArray will suffice.
<!-- YAML
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-->
```C
napi_status napi_create_buffer_copy(napi_env env,
size_t length,
const void* data,
void** result_data,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] size`: Size in bytes of the input buffer (should be the same as the
size of the new buffer).
- `[in] data`: Raw pointer to the underlying buffer to copy from.
- `[out] result_data`: Pointer to the new Buffer's underlying data buffer.
- `[out] result`: A `napi_value` representing a `node::Buffer`.
Returns `napi_ok` if the API succeeded.
This API allocates a `node::Buffer` object and initializes it with data copied
from the passed-in buffer. While this is still a fully-supported data
structure, in most cases using a TypedArray will suffice.
<!-- YAML
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```C
napi_status napi_create_external(napi_env env,
void* data,
napi_finalize finalize_cb,
void* finalize_hint,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] data`: Raw pointer to the external data.
- `[in] finalize_cb`: Optional callback to call when the external value
is being collected.
- `[in] finalize_hint`: Optional hint to pass to the finalize callback
during collection.
- `[out] result`: A `napi_value` representing an external value.
Returns `napi_ok` if the API succeeded.
This API allocates a JavaScript value with external data attached to it. This
is used to pass external data through JavaScript code, so it can be retrieved
later by native code. The API allows the caller to pass in a finalize callback,
in case the underlying native resource needs to be cleaned up when the external
JavaScript value gets collected.
*Note*: The created value is not an object, and therefore does not support
additional properties. It is considered a distinct value type: calling
`napi_typeof()` with an external value yields `napi_external`.
<!-- YAML
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-->
```C
napi_status
napi_create_external_arraybuffer(napi_env env,
void* external_data,
size_t byte_length,
napi_finalize finalize_cb,
void* finalize_hint,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] external_data`: Pointer to the underlying byte buffer of the
ArrayBuffer.
- `[in] byte_length`: The length in bytes of the underlying buffer.
- `[in] finalize_cb`: Optional callback to call when the ArrayBuffer is
being collected.
- `[in] finalize_hint`: Optional hint to pass to the finalize callback
during collection.
- `[out] result`: A `napi_value` representing a JavaScript ArrayBuffer.
Returns `napi_ok` if the API succeeded.
This API returns an N-API value corresponding to a JavaScript ArrayBuffer.
The underlying byte buffer of the ArrayBuffer is externally allocated and
managed. The caller must ensure that the byte buffer remains valid until the
finalize callback is called.
JavaScript ArrayBuffers are described in
[Section 24.1](https://tc39.github.io/ecma262/#sec-arraybuffer-objects)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_external_buffer(napi_env env,
size_t length,
void* data,
napi_finalize finalize_cb,
void* finalize_hint,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] length`: Size in bytes of the input buffer (should be the same as
the size of the new buffer).
- `[in] data`: Raw pointer to the underlying buffer to copy from.
- `[in] finalize_cb`: Optional callback to call when the ArrayBuffer is
being collected.
- `[in] finalize_hint`: Optional hint to pass to the finalize callback
during collection.
- `[out] result`: A `napi_value` representing a `node::Buffer`.
Returns `napi_ok` if the API succeeded.
This API allocates a `node::Buffer` object and initializes it with data
backed by the passed in buffer. While this is still a fully-supported data
structure, in most cases using a TypedArray will suffice.
*Note*: For Node.js >=4 `Buffers` are Uint8Arrays.
<!-- YAML
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-->
```C
napi_status napi_create_function(napi_env env,
const char* utf8name,
size_t length,
napi_callback cb,
void* data,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] utf8name`: A string representing the name of the function encoded as
UTF8.
- `[in] length`: The length of the utf8name in bytes, or
NAPI_AUTO_LENGTH if it is null-terminated.
- `[in] cb`: A function pointer to the native function to be invoked when the
created function is invoked from JavaScript.
- `[in] data`: Optional arbitrary context data to be passed into the native
function when it is invoked.
- `[out] result`: A `napi_value` representing a JavaScript function.
Returns `napi_ok` if the API succeeded.
This API returns an N-API value corresponding to a JavaScript Function object.
It's used to wrap native functions so that they can be invoked from JavaScript.
JavaScript Functions are described in
[Section 19.2](https://tc39.github.io/ecma262/#sec-function-objects)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_object(napi_env env, napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[out] result`: A `napi_value` representing a JavaScript Object.
Returns `napi_ok` if the API succeeded.
This API allocates a default JavaScript Object.
It is the equivalent of doing `new Object()` in JavaScript.
The JavaScript Object type is described in
[Section 6.1.7](https://tc39.github.io/ecma262/#sec-object-type) of the
ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_symbol(napi_env env,
napi_value description,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] description`: Optional napi_value which refers to a JavaScript
String to be set as the description for the symbol.
- `[out] result`: A `napi_value` representing a JavaScript Symbol.
Returns `napi_ok` if the API succeeded.
This API creates a JavaScript Symbol object from a UTF8-encoded C string
The JavaScript Symbol type is described in
[Section 19.4](https://tc39.github.io/ecma262/#sec-symbol-objects)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_typedarray(napi_env env,
napi_typedarray_type type,
size_t length,
napi_value arraybuffer,
size_t byte_offset,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] type`: Scalar datatype of the elements within the TypedArray.
- `[in] length`: Number of elements in the TypedArray.
- `[in] arraybuffer`: ArrayBuffer underlying the typed array.
- `[in] byte_offset`: The byte offset within the ArrayBuffer from which to
start projecting the TypedArray.
- `[out] result`: A `napi_value` representing a JavaScript TypedArray.
Returns `napi_ok` if the API succeeded.
This API creates a JavaScript TypedArray object over an existing ArrayBuffer.
TypedArray objects provide an array-like view over an underlying data buffer
where each element has the same underlying binary scalar datatype.
It's required that (length * size_of_element) + byte_offset should
be <= the size in bytes of the array passed in. If not, a RangeError exception is
raised.
JavaScript TypedArray Objects are described in
[Section 22.2](https://tc39.github.io/ecma262/#sec-typedarray-objects)
of the ECMAScript Language Specification.
<!-- YAML
added: v8.3.0
-->
```C
napi_status napi_create_dataview(napi_env env,
size_t byte_length,
napi_value arraybuffer,
size_t byte_offset,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] length`: Number of elements in the DataView.
- `[in] arraybuffer`: ArrayBuffer underlying the DataView.
- `[in] byte_offset`: The byte offset within the ArrayBuffer from which to
start projecting the DataView.
- `[out] result`: A `napi_value` representing a JavaScript DataView.
Returns `napi_ok` if the API succeeded.
This API creates a JavaScript DataView object over an existing ArrayBuffer.
DataView objects provide an array-like view over an underlying data buffer,
but one which allows items of different size and type in the ArrayBuffer.
It is required that `byte_length + byte_offset` is less than or equal to the
size in bytes of the array passed in. If not, a RangeError exception is raised.
JavaScript DataView Objects are described in
[Section 24.3][] of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_int32(napi_env env, int32_t value, napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: Integer value to be represented in JavaScript.
- `[out] result`: A `napi_value` representing a JavaScript Number.
Returns `napi_ok` if the API succeeded.
This API is used to convert from the C `int32_t` type to the JavaScript
Number type.
The JavaScript Number type is described in
[Section 6.1.6](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_uint32(napi_env env, uint32_t value, napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: Unsigned integer value to be represented in JavaScript.
- `[out] result`: A `napi_value` representing a JavaScript Number.
Returns `napi_ok` if the API succeeded.
This API is used to convert from the C `uint32_t` type to the JavaScript
Number type.
The JavaScript Number type is described in
[Section 6.1.6](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_int64(napi_env env, int64_t value, napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: Integer value to be represented in JavaScript.
- `[out] result`: A `napi_value` representing a JavaScript Number.
Returns `napi_ok` if the API succeeded.
This API is used to convert from the C `int64_t` type to the JavaScript
Number type.
The JavaScript Number type is described in
[Section 6.1.6](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type)
of the ECMAScript Language Specification. Note the complete range of `int64_t`
cannot be represented with full precision in JavaScript. Integer values
outside the range of
[`Number.MIN_SAFE_INTEGER`](https://tc39.github.io/ecma262/#sec-number.min_safe_integer)
-(2^53 - 1) -
[`Number.MAX_SAFE_INTEGER`](https://tc39.github.io/ecma262/#sec-number.max_safe_integer)
(2^53 - 1) will lose precision.
<!-- YAML
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```C
napi_status napi_create_double(napi_env env, double value, napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: Double-precision value to be represented in JavaScript.
- `[out] result`: A `napi_value` representing a JavaScript Number.
Returns `napi_ok` if the API succeeded.
This API is used to convert from the C `double` type to the JavaScript
Number type.
The JavaScript Number type is described in
[Section 6.1.6](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-number-type)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_string_latin1(napi_env env,
const char* str,
size_t length,
napi_value* result);
```
- `[in] env`: The environment that the API is invoked under.
- `[in] str`: Character buffer representing a ISO-8859-1-encoded string.
- `[in] length`: The length of the string in bytes, or
NAPI_AUTO_LENGTH if it is null-terminated.
- `[out] result`: A `napi_value` representing a JavaScript String.
Returns `napi_ok` if the API succeeded.
This API creates a JavaScript String object from a ISO-8859-1-encoded C string.
The JavaScript String type is described in
[Section 6.1.4](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_create_string_utf16(napi_env env,
const char16_t* str,
size_t length,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] str`: Character buffer representing a UTF16-LE-encoded string.
- `[in] length`: The length of the string in two-byte code units, or
NAPI_AUTO_LENGTH if it is null-terminated.
- `[out] result`: A `napi_value` representing a JavaScript String.
Returns `napi_ok` if the API succeeded.
This API creates a JavaScript String object from a UTF16-LE-encoded C string
The JavaScript String type is described in
[Section 6.1.4](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type)
of the ECMAScript Language Specification.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_create_string_utf8(napi_env env,
const char* str,
size_t length,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] str`: Character buffer representing a UTF8-encoded string.
- `[in] length`: The length of the string in bytes, or NAPI_AUTO_LENGTH
if it is null-terminated.
- `[out] result`: A `napi_value` representing a JavaScript String.
Returns `napi_ok` if the API succeeded.
This API creates a JavaScript String object from a UTF8-encoded C string
The JavaScript String type is described in
[Section 6.1.4](https://tc39.github.io/ecma262/#sec-ecmascript-language-types-string-type)
of the ECMAScript Language Specification.
<!-- YAML
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```C
napi_status napi_get_array_length(napi_env env,
napi_value value,
uint32_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing the JavaScript Array whose length is
being queried.
- `[out] result`: `uint32` representing length of the array.
Returns `napi_ok` if the API succeeded.
This API returns the length of an array.
Array length is described in
[Section 22.1.4.1](https://tc39.github.io/ecma262/#sec-properties-of-array-instances-length)
of the ECMAScript Language Specification.
<!-- YAML
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-->
```C
napi_status napi_get_arraybuffer_info(napi_env env,
napi_value arraybuffer,
void** data,
size_t* byte_length)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] arraybuffer`: `napi_value` representing the ArrayBuffer being queried.
- `[out] data`: The underlying data buffer of the ArrayBuffer.
- `[out] byte_length`: Length in bytes of the underlying data buffer.
Returns `napi_ok` if the API succeeded.
This API is used to retrieve the underlying data buffer of an ArrayBuffer and
its length.
*WARNING*: Use caution while using this API. The lifetime of the underlying data
buffer is managed by the ArrayBuffer even after it's returned. A
possible safe way to use this API is in conjunction with [`napi_create_reference`][],
which can be used to guarantee control over the lifetime of the
ArrayBuffer. It's also safe to use the returned data buffer within the same
callback as long as there are no calls to other APIs that might trigger a GC.
<!-- YAML
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-->
```C
napi_status napi_get_buffer_info(napi_env env,
napi_value value,
void** data,
size_t* length)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing the `node::Buffer` being queried.
- `[out] data`: The underlying data buffer of the `node::Buffer`.
- `[out] length`: Length in bytes of the underlying data buffer.
Returns `napi_ok` if the API succeeded.
This API is used to retrieve the underlying data buffer of a `node::Buffer`
and it's length.
*Warning*: Use caution while using this API since the underlying data buffer's
lifetime is not guaranteed if it's managed by the VM.
<!-- YAML
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-->
```C
napi_status napi_get_prototype(napi_env env,
napi_value object,
napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] object`: `napi_value` representing JavaScript Object whose prototype
to return. This returns the equivalent of `Object.getPrototypeOf` (which is
not the same as the function's `prototype` property).
- `[out] result`: `napi_value` representing prototype of the given object.
Returns `napi_ok` if the API succeeded.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_typedarray_info(napi_env env,
napi_value typedarray,
napi_typedarray_type* type,
size_t* length,
void** data,
napi_value* arraybuffer,
size_t* byte_offset)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] typedarray`: `napi_value` representing the TypedArray whose
properties to query.
- `[out] type`: Scalar datatype of the elements within the TypedArray.
- `[out] length`: Number of elements in the TypedArray.
- `[out] data`: The data buffer underlying the typed array.
- `[out] byte_offset`: The byte offset within the data buffer from which
to start projecting the TypedArray.
Returns `napi_ok` if the API succeeded.
This API returns various properties of a typed array.
*Warning*: Use caution while using this API since the underlying data buffer
is managed by the VM
<!-- YAML
added: v8.3.0
-->
```C
napi_status napi_get_dataview_info(napi_env env,
napi_value dataview,
size_t* byte_length,
void** data,
napi_value* arraybuffer,
size_t* byte_offset)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] dataview`: `napi_value` representing the DataView whose
properties to query.
- `[out] byte_length`: Number of bytes in the DataView.
- `[out] data`: The data buffer underlying the DataView.
- `[out] arraybuffer`: ArrayBuffer underlying the DataView.
- `[out] byte_offset`: The byte offset within the data buffer from which
to start projecting the DataView.
Returns `napi_ok` if the API succeeded.
This API returns various properties of a DataView.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_bool(napi_env env, napi_value value, bool* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript Boolean.
- `[out] result`: C boolean primitive equivalent of the given JavaScript
Boolean.
Returns `napi_ok` if the API succeeded. If a non-boolean `napi_value` is
passed in it returns `napi_boolean_expected`.
This API returns the C boolean primitive equivalent of the given JavaScript
Boolean.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_double(napi_env env,
napi_value value,
double* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript Number.
- `[out] result`: C double primitive equivalent of the given JavaScript
Number.
Returns `napi_ok` if the API succeeded. If a non-number `napi_value` is passed
in it returns `napi_number_expected`.
This API returns the C double primitive equivalent of the given JavaScript
Number.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_external(napi_env env,
napi_value value,
void** result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript external value.
- `[out] result`: Pointer to the data wrapped by the JavaScript external value.
Returns `napi_ok` if the API succeeded. If a non-external `napi_value` is
passed in it returns `napi_invalid_arg`.
This API retrieves the external data pointer that was previously passed to
`napi_create_external()`.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_int32(napi_env env,
napi_value value,
int32_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript Number.
- `[out] result`: C int32 primitive equivalent of the given JavaScript Number.
Returns `napi_ok` if the API succeeded. If a non-number `napi_value`
is passed in `napi_number_expected .
This API returns the C int32 primitive equivalent
of the given JavaScript Number. If the number exceeds the range of the
32 bit integer, then the result is truncated to the equivalent of the
bottom 32 bits. This can result in a large positive number becoming
a negative number if value is > 2^31 -1.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_int64(napi_env env,
napi_value value,
int64_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript Number.
- `[out] result`: C int64 primitive equivalent of the given JavaScript Number.
Returns `napi_ok` if the API succeeded. If a non-number `napi_value`
is passed in it returns `napi_number_expected`.
This API returns the C int64 primitive equivalent of the given
JavaScript Number
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_string_latin1(napi_env env,
napi_value value,
char* buf,
size_t bufsize,
size_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript string.
- `[in] buf`: Buffer to write the ISO-8859-1-encoded string into. If NULL is
passed in, the length of the string (in bytes) is returned.
- `[in] bufsize`: Size of the destination buffer. When this value is
insufficient, the returned string will be truncated.
- `[out] result`: Number of bytes copied into the buffer, excluding the null
terminator.
Returns `napi_ok` if the API succeeded. If a non-String `napi_value`
is passed in it returns `napi_string_expected`.
This API returns the ISO-8859-1-encoded string corresponding the value passed
in.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_string_utf8(napi_env env,
napi_value value,
char* buf,
size_t bufsize,
size_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript string.
- `[in] buf`: Buffer to write the UTF8-encoded string into. If NULL is passed
in, the length of the string (in bytes) is returned.
- `[in] bufsize`: Size of the destination buffer. When this value is
insufficient, the returned string will be truncated.
- `[out] result`: Number of bytes copied into the buffer, excluding the null
terminator.
Returns `napi_ok` if the API succeeded. If a non-String `napi_value`
is passed in it returns `napi_string_expected`.
This API returns the UTF8-encoded string corresponding the value passed in.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_string_utf16(napi_env env,
napi_value value,
char16_t* buf,
size_t bufsize,
size_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript string.
- `[in] buf`: Buffer to write the UTF16-LE-encoded string into. If NULL is
passed in, the length of the string (in 2-byte code units) is returned.
- `[in] bufsize`: Size of the destination buffer. When this value is
insufficient, the returned string will be truncated.
- `[out] result`: Number of 2-byte code units copied into the buffer, excluding the null
terminator.
Returns `napi_ok` if the API succeeded. If a non-String `napi_value`
is passed in it returns `napi_string_expected`.
This API returns the UTF16-encoded string corresponding the value passed in.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_value_uint32(napi_env env,
napi_value value,
uint32_t* result)
```
- `[in] env`: The environment that the API is invoked under.
- `[in] value`: `napi_value` representing JavaScript Number.
- `[out] result`: C primitive equivalent of the given `napi_value` as a
`uint32_t`.
Returns `napi_ok` if the API succeeded. If a non-number `napi_value`
is passed in it returns `napi_number_expected`.
This API returns the C primitive equivalent of the given `napi_value` as a
`uint32_t`.
<!-- YAML
added: v8.0.0
-->
```C
napi_status napi_get_boolean(napi_env env, bool value, napi_value* result)
```
- `[in] env`: The environment that the API is invoked under.
- …
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@SwathiKalahastri Thanks so much for your first commit 🎉. Landed as |
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PR-URL: #16911 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
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PR-URL: #16911 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
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PR-URL: #16911 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
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PR-URL: nodejs#16911 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
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Backport-PR-URL: #19447 PR-URL: #16911 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
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Checklist
make -j4 test(UNIX), orvcbuild test(Windows) passesAffected core subsystem(s)
My first pr to nodejs. Thanks.
EDIT: deleted some long text that was pasted wrongly. apologies.